Electrochemical Synthesis Of Tetra Alkvl Phosphonium Hydroxide

Due to its good stability and lower toxicity,tetra alkyl phosphonium hydroxide has a wide application prospect in the cleaning,etching and developing processes during the production of circuit boards.With the rapid development of the electronics industry and the high degree of intensification of semiconductor devices,the demand for electronic grade tetra alkyl phosphonium hydroxide will increase rapidly in the future.At present,there are few studies on the tetra alkyl phosphonium hydroxide,and most of the preparation methods are synthesized by chemical method.So,in this paper,the feasibility of using ion-exchange membrane electrolysis method to prepare tetra alkyl phosphonium hydroxide was discussed.The process conditions and the factors affecting the purity during the electrolysis were studied systematically.In this paper,tetra methyl phosphonium bromide was prepared by ion-exchange membrane electrolysis with tetra methyl phosphonium bromide as the starting material.The electrocatalytic activities of carbon felts,graphite and coated titanium electrodes on the redox of Br2/Br-were investigated.The experimental results show that the carbon felt electrode has best electrocatalytic activity to redox of Br2/Br-,and it's performance can be further enhanced after heat treated at 500? in air.The effects of Nafion115 cationic membrane,Nafion117 cationic membrane,NepemN115 cationic membrane,JCM-II cationic membrane,QQ-YLM001 cationic membrane,microporous membrane and JCM-II anionic membrane on the cell voltage in electrolysis were also investigated.It is found that JCM-II cationic membrane is a better ion membrane for electrolytic tetra methyl phosphonium hydroxide.Finally,the effects of electrolysis factors such as power generation,raw material concentration and current density on the current efficiency and energy consumption during the electric synthesis process were investigated.It is found that the better current efficiency,lower energy consumption and faster of the electrolysis rate were got when the raw material concentration is 0.75 mol.L-1,the current density is 40 mA.cm-2,the power is 60% of the theoretical power.Under this condition,the current efficiency is 74.67%,the energy consumption is 2.67 kW.h.Kg-1,the electrolysis rate is8.36×10-5mol.min-1.The results of infrared spectroscopy and nuclear magnetic resonance(NMR)show that the products obtained by electrolysis are tetra methyl phosphonium hydroxide.On the basis of this,the electrolytic properties of tetra alkyl phosphonium bromide withdifferent alkyl chain lengths were also investigated in the electrolytic cells separated from the anionic and cationic membranes.It was found that the resistance of the positive ions through the separator was increased at any time due to the increase of the alkyl chain to the positive ion size,so that when the tetra alkyl phosphonium bromide was electrolyzed in the electrolytic cell separated by the cationic membrane,the decrease of the current efficiency,the increase of the energy consumption and the decrease of the electrolysis rate with the increase of the chain length.It was also found that the electrolytic tetra alkyl phosphonium bromide used in the electrolytic cell separated by the anionic membrane had lower cell pressure,but with this electrolysis,the product separation and purification is difficult because of the reactants and products are in the cathode chamber,so it is not suitable for the preparation of high purity products.The effect of the electrolysis conditions on the purity of the product was also investigated and tested by ion chromatography.The results showed that the type of membrane,electrolysis time,and current density have a greater impact on the bromine ion content.Under the JCM-?homogeneous cation exchange membrane,when the electrolysis time is 60% of the theoretical time and the current density is 60 mA.cm-2,the transmittance of bromide ions is less.This provides a technical guarantee for the optimization of the electrochemical synthesis conditions of the tetra alkyl phosphonium hydroxide,the production process control and the product quality monitoring.